Timer and synchronizing signal generator



July 18, 1950 E. H. scHoENFELD 'um AND sYNcx-moNIzING SIGNAL GENERATORFiled July 11, 194s 13 Sheets-Sheet 1 u S n .w 55m. E S Qx NQ INVENTOREARL H. scHoENFELD ATTORNEY July 18, 1950 E. H. scHoENFELD 2,515,613

um AND sYNcHRoNIzING SIGNAL GENERATOR Filed July 11, 194s 1ssheets-sheet 2 -wizur 1 INVENTOR EARL H. SCHOENFELD ATTORNEY July 18,1950 E. H. scHoENFELD 2,515,613

TIKER AND SYNCHRONIZING SIGNAL GENERATOR Filed July 11. 1946 13Sheets-Sheet 3 EARL H. SCHOENf-ELD ATTORN EY July 18, 1950 E. H.scHol-:NFELD 'mma mn sxmclmonrzmc SIGNAL GENERATOR Filed July 11, 194s13 Sheets-Sheet 4 July 18, 1950 E. H. scHoENFELD TIIIER ANDSYNCHRONIZING SIGNAL GENERATOR Filed July 11. 194e 13 Sheets-Sheet 5ATTORNEY E. H. scHoENFELD 2,515,613

TIMER AND sYNcRRoNIzING SIGNAL GENERATOR Filed July 11, 1946 July 18,1950 15 Sheets-Sheet 6 31.5 KC [33 /IVPl/T `C'L /PPER EOI/7,007

+250 V /54 22K /53 4 70K INVEN TOR EARL H. .SCHOENFELD ATTORNEY E. H.SCHOENFELD TIMER AND SYNCHRONIZING SIGNAL GENERATOR IAI R m Y m e u N FR E N O v n m s A L R nu i u Y B SSS tm w+ @ESS E .M WPm .WIW W ||\|hw|WWNV v .m mm S im( 1.1.1.1. Nm`k A m S A Ess n" mw\\ w NQ ma Lf. G+ Wk`July 18, 1950 Filed July 11, 194s E. H. SCHOENFELD TIMER ANDSYNCHRONIZING SIGNAL GENERATOR July 1s, 195o 13 Sheets-Sheet 8 FiledJuly l1, 1946 INVENTORS EARL ILSCHOENFELD TTORNEY @EAS July 18, 1950 aH. scHoENFELD 'mma um sYNcmzoNIzING SIGNAL GENERATOR 13 Sheets-Sheet 9Filed July 11, 1946 EARL H. s'cHoE'NFELD gaa/w ATTORNEY .hmul r July 18,1950 E. H. scHox-:NFELD TIMER AND sYNcHRoNIzING SIGNAL GENERATOR FiledJuly 11, 1946 13 Sheets-Sheet 10 Immfil -hmw umit N bmw S :Si MN mvENToREARL H. SCHOENFELD ATTORNEY 13 Sheets-Sheet ll July 18, 1950 E. H.scHoENFELD 'I'Im AND SYNCl-IRONIZING SIGNAL GENERATOR med July 11, 1946July 18, 1950 E. H. scHoENFELD TIMER AND SYNCHRONIZING SIGNAL GENERATORFiled .my 11, 194e 13 Sheets-Sheet 12 'fn'- u amsn keum.

INVENTOR am. H. scHoeNFeLn ATTORNEY July 18, 1950 E. H. scHoENl-'ELDTIIER AND SYNCHRONIZING SIGNAL GENERATOR med .my 11, 194s 13Sheets-Sheet 13 Patented July 18, 1950 TIMER AND SYN CHRONIZING SIGNALGENERATOR Earl H. Schoenfeld, Mamaroneck, N. Y., assignor to RadioCorporation of America, a corporation of Delaware Application July 11,1946, Serial No. 682,738 19 claims. (ci. 17a-69.5)

My invention relates in general to apparatus for developing electricalsignals and more particularly to apparatus for developing equalizing,synchronizing, driving, and blanking signals for television apparatus.

In the art of television transmission it is necessary to synchronizeaccurately the action of the apparatus which is doing the scansion ofthe image televised and the action of the appara.- tus for reproducingthe image. Presently known television apparatus usually accomplishesboth the scansion and the reproduction of a televised image by means ofa moving cathode ray beam which is moved line by line over a surfaceundergoing scanslon in the case of the transmitter, and over a surfacefor reproducing the image in the case of the receiver. The back andforth movement of the electron beams at the transmitter and receiverdemand a fine degree of synchronized operation. Accordingly it is one ofthe objects of my invention to provide apparatus for generating signalsfor accomplishing the proper synchronization between the movement of acathode ray forming part of a transmission apparatus and the cathode raybeam forming part of a television receiving apparatus.

Usually scansion is accomplished in onedirection of movement of thecathode ray beamV only and the action of the cathode ray beam is negatedduring its return to the initial portion either of a line, or of afield, or a complete frame, in order to prevent the production of wellknown, undesired effects. This is accomplished by a blanking of thecathode ray beam during its return to an initial point from whichscansion or reproduction then again takes place. Accordingly it isanother of the objects of my invention to provide a method of, andapparatus for, developeng proper blanking control signals for use bothat the transmitter and at the receiver.

.Apparatus for generating synchronizing, and blanking signals andequalizing signals and driving signals are well known to the prior artin the art to which this ca 'se pertains. This apparatus has, however,suffered from the disadvantage that it has been extremely diflicult tomaintain proper 4phasing between the various signals comprising thesynchronizing, driving, blanking and equalizing signals. Thesedisadvantages have been overcome in the present invention andaccordingly it is another of the objects of my invention to provide amethod of, and apparatus for generating such signals, for use intelevision apparatus in which the initiation thereof, or in other wordsthe leading edge of each signal, will be generated under the control ofrepetitive signals having a definite fixed phase, and which thereforewill insure correct phase relationships between the various signalsdeveloped.

The prior art to which this case belongs has heretofore attempted to xthe phase of each of the signals hereinbefore referred to by separatelygenerating the signals and then combining them. Manual adjustments havebeen necessary in order to correct for inaccurate phasing of any ofthese signals. This is a delicate operation and it is not an absolutelystable operation. It is, therefore, another of the objects of my1nvention to provide an apparatus for generating synchronizing,blanking, and equalizing signals in which manual adjustments aresubstantially eliminated.

It is another of the objects of my invention to provide an apparatus fordeveloping synchronizing and blanking signals which are definitelylocked in together in phase.

It is a, still further object of my invention to provide apparatus fordeveloping synchronizing and blanking signals both for the transmissionapparatus and the receiving apparatus.

Other objects will be apparent from a review of the subject matter setforth hereinafter.

In general my apparatus is particularly adaptable for developingsynchronizing, equalizing, and blanking signals for use in-an odd lineinterlaced type of television transmission. Present standardscontemplate the use of 525 lines to the complete image with alternateline interlacing accomplished at the rate of interlaced fields to thecomplete image, or a transmission speed of 30 complete images persecond.

My invention contemplates the' development of a series of xed phase,very steep pulses of a frequency of 31,500 cycles (double the assumedline frequency), and the horizontal synchronizing pulses for both thetransmitter and receiver, the vertical synchronizing pulses, thehorizontal and vertical blanking pulses for the transmitter andreceiver, and the equalizing signals, all are developed under theinfluence of this single recurring set of sharp pulses or pips of fixedphase.

The 31,500 cycle sharp pulses are impressed onto a delay line having aseries of taps and hence there will appear at the various taps sets ofpulses, or pips, having predetermined phase relationships, and having avery steep front. These pips are used in some instances to control thedevelopment of the trailing edge of some of the developed signals, andin all cases to initiate The horizontal synchronizing signals for thereceiver, the two sets of equalizing signals and the verticalsynchronizing signals all are deponents thereof are representative of ascanned line of television image. The complete signal containshorizontal synchronizing signals as well as video components, and forillustrative purposes there is shown also the vertical synchro- \nizingsignals developed at the end of the scanveloped by a single signalgenerator under the control of the 31.5 k. c. pips from the delay line,thus assuring accuracy in relative phasing.

Further, apparatus is provided which. under the influence of the steeppulses taken from the delay line,'will control the development of theproper number of equalizing and synchronizing pulses and this will beexplained more fully hereinafter in this specification.

In addition to the apparatus for generating the horizontal synchronizingpulses for both the transmitter and receiver, the horizontal andvertical blanking pulses for the transmitter and receiver, and theequalizing signals, there is provided a timer unit which is adapted togenerate a 31.5 k. c. sine wave signal and from this signal there isderived, by a set of frequency dividers, a 60 cycle signal having adefinite phase relationship with that of the sine wave. The 60 cyclesignal is then utilized to Aderive signals bearing a desiredrelationship to the iield scansion frequency. The timer unit alsoprovides among other signals, a 60 cycle rectangular pulse from the 60cycle signal and having one of the components thereof of apredeterminable length which is substantially two scanning lines lengthin duration and which can be used to advantage in the synchronizing andblanking signal generator component of this invention. The timer also isarranged so that, if absolutely necessary, a 60 cycle power line inputlcouldA be utilized in conjunction therewith.

My invention will best be understood by re ferring to the drawings, inwhich:

ards.

Fig.l, parts (a) Aand (b) thereof, is a showing y Aof a wave formrelating to odd line interlaclng television timer unit in accordancewith my invention.

Fig. 6 is a schematic diagram of a circuit for producing high frequencypulses, or pips, having very steep wave fronts;

Fig. '7 is a form of an on-off multivibrator circuit;

Fig. 8 is a multivibrator for producing a 60 cycle rectangular wave formhaving a component equal to 2H;

Fig. 9 is a showing of a pair of co-acting multivibrators.

Fig. 10, sections (a) and (b) thereof, is a circuit diagram of a timerunit in accordance with the invention;

Fig. 1l, sections (a) to (d) thereof is a circuit diagram of thesynchronizing and blanking generator.

Referring to Fig. 1, parts (a) and (b) thereof, there is shown arepresentation of a portion of a transmitted televisional signal. Thevideo comsion of each scanned eld. Equalizlng, vertical synchronizing,and blanking signals are a component part of the latter signal. This isa form of transmission which meets present RMA stand- In these curves anegative form of transmission is represented, that is to say that thesmallest amplitude of carrier is radiated as a repre-l sentation ofpicture white. The blanking level is indicated, and the horizontalsynchronizing signals are transmitted simultaneously with the horizontalblanking signals, the two together forming a pedestal-like structure.Interposed between these signals is the picture or video signal. Aftereach interlaced iield there is transmitted a signal which-'comprises anequalizing pulse interval during which there are transmitted 6equalizing signals, then a vertical synchronizing pulse interval duringwhich 6 vertical synchronizing signals are transmitted, and a secondequalizing pulse interval during which 6 equalizing pulses again aretransmitted. Horlzontal synchronizing signal transmission then isresumed before the scansion of a new iield takes place and, at the endof the vertical blanking interval, linear scansion recommences.

The wave form has been shown in two portions identified as (a) and (b)to show relative phase relationships between the signals identified witheach scanned field, it being assumed that an odd line interlaced form ofscanning will take place. Since 525 scanned lines comprise the completepicture, and 60 interlaced ilelds are transmitted per second, there willbe a phase displacement between the signals of the two fields comprisingthe complete picture. y

Referring to Fig. 2 there is shown a set of explanatory curvesshowingvarious pulses developed in the generation of the synchronizingand equalizing signals transmitted, and indicating the phaserelationships between the-various signals making up this set. Forpurposes of clarity and ease of illustration, some of these curves havebeen broken away in parts vand this has been indicated in the drawings.The 'derivation of these curves and their relationship each to the otherwill be explained more fully hereinafter in the specification inexplaining the operation of the apparatus involved.

, Referring to Fig. 3 there is shown a further set f explanatory curvesand these represent some of the developed wave formations occurringduring generation of the various signals by the timer and thesynchronizing generator as will be explained hereinafter in thisspecication. The relative phases of these curves are shown and in somecases thecurves have been broken away for purposes of clarity and fromspace considerations. This sequence of curves will be referred t0 morefully hereinafter during the explanation of the operation of theapparatus.

Referring to Fig. 4 there is shown a schematic block diagramillustrating the portion of my invention devoted to the generation ofthe synchronizing signals for use both at the transmitter and at thereceiver and the blanking signals for use at the receiver in atelevision system.

A 31,500 cycle generator (not shown) has a portion of the output thereofimpressed onto .a pulse generator I and the output of the pulse gen.

sixteen 0.08 microsecond time-delay sections, l

thereby providing an overall maximum delay of, 12.8 microseconds. Thedelay vline sectionsywere each made up of two coils wound on separateiron cores, which are separated by 0.025 inch in order to provide thedesired amount of coupling. The iron cores were made so that they couldbe mounted by sliding them on a thin Bakelite rod.,

Spacers one half inchlong were placed between adjacent sections toprevent any appreciable magnetic coupling across the entire section. Onesuch row of coils was placed along the top and another along the bottomof each panel and the condensers lwere mounted between. The two coils ofa section were connected so that ,theywere series aiding with a 100micromicrofarad condenser -connected from their ij iuictionto ground.

The inductance of each coil lori iironcorewas 26 microhenrys and atoleranceof plus or minus in value for both the coilsand condenser-sgave very satisfactory results. Thesections on all ten panels wereconnected in series and terminated with 8009. (A variable resistance of0-10009 was used and adjusted for zero reflection). Taps were taken atpoints along the line to provide the desired time delays. In this iigurethe line =has been given reference numerals representative of the numberof sections Iof line from the beginning or input to the particular tapwhich is numbered.

Signals from the tap I I are fed to a gate circuit I5 which will beillustrated and explained more fully hereinafter in this specification,and the signals from this tap also are fed to a gate circuit I6. Thepurpose and operation of the latter gate also will be explained morefully hereinafter.

Signals from the tap 46 on the delay line are impressed onto a gatecircuit I8 which is a gate to delete alternate horizontal blankingsignal trig.. gering signals and which will be explained more fullyhereinafter.

Signals from tap 'I3 on the delay line are impressed, by means of lead54, onto a clipping and phase inverting circuit and the output of thelatter circuit is impressed onto the synchronizing generator 2|, theoutput of the latter being impressed upon a gate circuit 22 and thenceto a clipping circuit 23;

Signals from the tap 85 are impressed onto a gate circuit 24 and signalsfrom tap II4 are impressed onto a gate circuit 25 and a gate circuit 26,both of which will be explained more fully hereinafter in referring tothe operation of the apparatus.

Another portion of the output from clipper circuit II is fed by way ofconductor 26 to inverting and amplifying circuit 21 and thence to adeleting multivibrator 28, the latter having one portion of its outputimpressed onto a gate circuit 29 and another portion thereof impressedonto gate I8, gate 30 and gate 26 via conductors 3| and 32 respectively.

Associated with the gate circuit I5 is a counter circuit 33, the latterbeing connected through conductor 34, to an inverting and amplifyingcircuit 36, which in turn is connected throughA conductor 36 to the oilterminal of 3 multivibrator units MV2, MV3, and MV4 which may be furtheridentified as the elements 38, 39, and 40 respectively.

The tap 68 on the delay line is connected through conductor 4I to amixing circuit 42 which has impressed onto the' input thereof a 60 cyclepulse which is rectangular in form and has a negative portionsubstantially equal to twice the line or horizontal scanning intervaland therefore is identied as a 2H pulse. The output of the mixingcircuit 42 is impressed onto a trigger circuit' 43 which is connected tothe "on terminal of a multivibrator MVI which may be further identifiedas the unit 44. The 01T terminal of MVI also is connected to. the onterminal of MV2 through conductor 4-5. An output or oi terminal of MV2is joined to the on terminal of MV3, and an output or oir terminal ofMV3 is connected to the on terminal of MV4. The o terminal of MV4 isconnected throughy conductor 48 to the off terminal of VMVI.

In referring to the on and oil terminals of thesemultivibrators, thefollowing should be kept in mind. The multivibrators are of themultistroke or non-self-restoring type. The output thereof is arectangular wave form and if the output is taken from one tube, theoutput of the other tube will be in reversed phase with respect to theiirst tube. The multivibrators are arranged so that they will beself-restoring after an interval of time relatively long compared to theoperating cycle of that portion of the invention of which they comprisea portion, hence they will be in the same receptive state .each time thecycle is started. This means then that a signal which flips or changesthe original operating state of the multivibrator may be said to haveturned it on and the signal which iiops or restores the multivibrator toits original operating state may be said to have turned it off. Outputpulses `may be taken from desired parts of the multivibrator inaccordance with the wave shape desired at a particular time.

The tap 68 on the delay line also is connected through conducting means50 to the input of the gate circuit 30, the latter being a gate fordeleting alternate horizontal' drive signals at the transmitter.k Thegate circuit 30 then is connected through conductor.5l to the generatorfor generating the horizontal driving signals at the transmitter, and,since it is assumed for purposes of illustration, that an iconoscopetype of tube may be used at the transmitter, the drawing of thegenerator 52 is identified as an "Iconoscope Horizontal Drive Generator.The horizontal drive generator 52 then is-connected to a clippingcircuit 53, the output 0f which goes to the driving means for theiconoscope (indicated but not shown).

For purposes of convenience there has been illustrated herein the legendindicating that an iconoscope type of tube is used as the transmittingtube and a kinescope type of tube used as a reproducing tube. This isfor purposes of convenience only and it will be appreciated that theselegends merely identify one type each of usable tubes. The imagedissector tube or monoscope, etc., might be used as well as reproducingtubes known by other particular trade marked names.

The tap II4 is connected through conductor 56 to the gate circuit 25which is a gate by establishing the rears of the developed horizontalsynchronizing signal. The tap III also is connected through conductor 51to the gate circuit 20 which is a gate for deleting alternate horizontaldrive triggering signals for the iconoscope.

There is provided, in addition, a generator for developing horizontalblanking signals which are transmitted with the vhorizontalsynchronizing signals and the gate circuit I8 feeds a portion of thetriggering pulses fed thereto by way of conductor 60 to the horizontalblanking signal generator 6|, the output of which goes to a mixingcircuit 62 where the horizontal blanking signals are mixed with thevertical blanking signals, the

latter having been generated in the vertical blanking generator 63 andconducted to the mixing circuit 62 by means of conductor 64. The mixedblanking signals then are fed through conductor 65 to a clipping circuit66 and the clipped signals then are delivered from the ele-l ment 66 asa composite blanking signal.

Referring tc Figure 5 there is shown an explanatory block diagram of atelevision timer unit which has been used in practicing my invention. A94.5 kilocycle oscillating crystal is connected in cooperativerelationship with a 31.5 kilocycle tuned oscillator I0|, the combinationforming a stabilized sine wave generator. Provision is made whereby anoscillator external to the apparatus may be inserted into the circuitIif desired. The output of the 31.5 k. c. synchronized oscillator then isfed through a 31.5 k. c. amplifier |02 and thence to the synchronizingand blanking generator unit of Figure 4.as indicated.

The 31.5 k. c. synchronized oscillator may then be locked in with the 60cycle supply by means of a phase discriminating circuit which' utilizesa reactance tube, for correcting for phase changes. A phasediscriminator detects the phase difference between the power linefrequency and the timer output frequency and where an undesired phasedifference occurs, the detector produces a direct current which, whenapplied to the grid of the reactance tube, causes a correction in the31.5 k. c. oscillator such as to bring the 31.5 k. c. oscillator `andthe 60 cycle supply power into definite, de-

sired phase relationship.

The 31.5 kilocycle pulses from the synchronizing and blanking signalgenerator may be fed to the timer as indicated by the lead |01 in Figure4 and these pulses pass through three frequency dividing circuits |08,|09 and I0, the combination of these dividers producing from the 31.5 k.c. pulses a square wave such as indicated and having a frequency of 60cycles.` These frequency dividers are of the type set forth in anapplication by Grosdoif filed March 1, 1945, Serial No. 580,446. A partof this 60 cycle output is fed via conductor ||2 through a delay circuitH3 and thence to the generator ||4 for generating the signal of thevertical iconoscope drive at the transmitter, the output of thisgenerator being fed through a clipping circuit ||5 to a utilizingcircuit, (indicated but not shown).

Another portion of the 60 cycle wave developed by the dividers is fedvia lead to a 30 cycle field separation 4circuit ||8 and a circuit IIS,the latter comprising a two line illuminating wave and sweep circuit,

From the synchronizing and blanking signal generator there may be drawnpulses having a half of the 31.5 kilocycle steep pulse frequency or a15.75 k. c. frequency signal, and these are passed through conductor 2|to the generator for generating the horizontal blanking pulses for theiconoscope tube at the transmitter and this circuit is identified as|22.

The conductor |00 leading to the synchronizing signal generator also isconnected to a generator |23 which develops the vertical iconoscopeblanking signals and the units |22 and |22 are both connected to circuit|24 which is a mixing circuit for mixing the iconoscope horizontalblanking signals and the iconoscope vertical blanking signals and thecomposite iconoscope blanking signals so formed are passed through aclipper |25 and thence to a utilization circuit (indicated but notshown).

The action of the apparatus is as follows:

It has been indicated hereinbefore in this specincation that one of themain objects of the invention is to provide an arrangement forgenerating or forming various signals used in television apparatus andwhich will maintain a constant phase relationship each with the other.Accordingly, the signals generated by this device evolve around thegeneration of a constant phase, very steep edged set of pulses or pips,which determine the generation of all of the signals developed by theapparatus. Accordingly, the sine wave generated by the synchronizedoscillator unit |'0| of Figure 5 is fed into pulse generator |0. Thisgenerator will be illustrated more fully hereinafter in Figure "6 ofthis specification.

The pulse generator |0 comprises a blocking oscillator which issynchronized in its operation with the sine Wave and, in addition, thevery sharp pulses formed bythe blocking oscillator effectively arecombined with the sine Wave and this combination is passed throughclipper circuit 'Ihe result is that from the clipper circuit there isput out a 31.5 kilocycle signal which is a very sharp steep edged pulseor as it may be termed a pip. This pulse as it is used in thedevelopment of various signals is represented in Figure 2 as curve bthereof. It is also indicated in the Figure 4 along side the conductori2 prior to its impression onto the delay line i3.

The signal will be delayed for differing periods of time in itstraversal of the delay line and the signal is 'utilized to control theleading edge of all of the generated signals in this apparatus. Sincethe 31.5 kilocycle pulse itself is a constant phase signal, it will beapparent that the leading edge of each of the generated signals mustmaintain a constant phase relationship.

In the development of the transmitted synchronizing signal thehorizontal synchronizing signals, the equalizing signals and thevertical synchronizing signals have the generation of both the leadingand trailing edges thereof controlled by this single 31.5 k. c.generated signal and all are developed by means of a singlelgenerator,thus assuring accuracy of phasev and doing away with manual control ofthe signal generator. By way of illustration, let it be assumed firstthat what is desired to be generated is the six equalizing signalsfollowed by the six vertical synchronizing signals which in turn isfollowed by six more equalizing signals.

Equalizing signalsI It can be assumed that the first six equalizingsignals may be generated in an interval between a time t1 and a time t2;that the vertical synchronizing signals are generated during an intervalbetween a time t2 and a time t; and the remaining six equalizing signalsmay be generated in an interval between the time ts and a time t4. Forpractical purposes it may be assumed that time t1 to tz, time t: to t:and time t: to t4 are equal intervals. In the practical embodiment ofthis invention, however, the time t1 to t2 is slightly less than theother two intervals and the reason forthis will be explained more fullyhereinafter. Hereinafter these intervals will be referred to as timetits; tats; and tati. l

Referring now'to the curves of Figure 2, the curve b represents thepulse which initiates the various signals or establishes the leadingvedge thereof, and this is taken from tap 13 on the delay line. The curvec represents the relative phase of the same signal as it appears at tapI and the signals from tap 85 will establish the rears of trailingedgesof the equalizing signals.

There has been shown impressed onto the element I2 a signal taken fromthe timer and which has a frequency of 60 cycles and has a negativeportion thereof which is substantially the duration of two scanninglines in length and this portion of the signal is referred to as 2H.This sig-v nal is shown as curve a in Figure 3. Since it is developedfrom the 31.5 k. c. steep edged signal generated, its phaseis xed. Nowif this signal be passed through a dilerentiating circuit (well known)the resulting signal will be of the form shown in curve b of Figure 3.The phase of this signal (and that of the negative 2H pulses) may beselected with respect to the phase of the 31.5 k. c. steep edged pulses`from the delay line. The relative phase of the two pulses is indicatedby curves b and c of Fig. 3. Now ifthe signals of curves b and c beadded the result is a curve shaped in the manner indicated by curve d ofvFig. 3. lNow if these signals be combined and the combined signal bepassed through a clipping circuit (well known) as indicated by thedashed line on curve d, the output of the clipping circuit will be aseries of very steep edged pulses or pips occurring sixty times persecond. It is the occurrence of this 60 cycle pulse which establishesthe time t1 hereinbefore referred to in this speciiication and this isindicated in curve e of Fig. 3. It will be appreciated that the polarityof this pulse may be selected. It is impressed as a negative pulse ontothe input of multivibrator MVI and MV2 to turn on or nip or to place ina definite operating state these two multivibrators.

Assume now that at the time t1, multivibrators MVI and MV2 are turnedon, that is to sayl are brought to a desired portion of their operatingcycle. These two multivibrators are of the socalled ilip-ilop ortriggered type and will remain on until triggered or turned off, orotherwise returned to their original State. A reference to Fig. 4 willshow that the circuit 24 will be gated under the influence of MV2 andalso MV4. Accordingly while MV2 is on or in one portion of its operatingcycle,I the gate 2l will be operative, a positive signal being impressedthereon. It also will be noted that the off terminal of MVZis controlledby circuit 33 through circuit 35, the former being identified as a 6counter. The 6 counter is a circuit of the type referred to in theapplication of Igor.Eugene Grosdofi, Serial No. 580,446, filed March 1,1945, and entitled "Elec- 10 will begin to operate. At the end of sixpulses impressed onto the 6 counter the latter will deliver a pulseto-MV2, MVS and MVI. Il.' any of these multivibrators is on then it willbe turned oi, or restored to an original state. Accordingly at the endof the iirst 6 pulses impressed on the 6 counter, MV2 will be turned oi.A 6 counter was selected because with the type of signal radiated thereare six equalizing .signals developed in two series o1' equalizingsignals, andsix vertical synchronizing signals. MV2 controls thegeneration of the 'ilrst series of equalizing signals. When MV2 isturned off the time tz has been identied.

The control of MV2 has been indicated by curve a" Vertical synchronizingpulses .At the time tz the multivibrator MV3 will be turned on (the oncontrol of this multivibrator being controlled by the change in voltageacross tron Counter and is a type of counter circuit a part of MV2 whenMV2 is opped or returned to its original state due to the action of the6 counter thereon). Now the 6 counter will allow MV3 to remain operable-until six more pulses of 31.5 k. c. frequency have'been impressed onthe counter and the time at which the 6 counter developes a second pulsedetermines `the time t3. The phase of the pulse determining the rearedge of the vertical synchronizing pulses is shown as curve a of Fig. 2.Since MV3 will remain operable during the interval tzts, gate i6 willremain operable during the same interval and the pulses from the tap I1will pass through gate I6 to generator 2l to establish the rear edges ofthe vertical synchronizing signal. During interval teta six of thesepulses will be developed. Thus the six vertical synchronizing pulsesfollow directly behind the first set of six equalizing pulses.

Second eqiualizing signals At the time t: the multivibrator MV4 will beturned on (the drop in the voltage across one part of MVS acting tooperate this multivibrator which is also of the ip-iiop type). Again the6 counter will allow MV4 to operate until six pulses have been impressedonto the counter. The action of MVl being similar to MV2, extendedexplanation is not considered necessary. MV4 will be turned off by the 6counter at a time t4. During the interval t3t4. gate 24 will be operableand six more equalizing pulses will be developed. However a part of thevoltage drop occurring when MV4 goes off is utilized to turn oil? MVI,all of these multivibrators being of a type so that their oscillatingcharacteristic is vsuch that one pulse impressedV thereon determinesoneportion of its cycle and they will remain in a changed state until asecond pulse re-establishes their initial state. This is, in general,true except as has been pointed out hereinbefore, a restoring condensermay be used to restore the mutivibrator after the lapse of a definitetime interval. It will be apparent that MVI has been operable during theentire time titl. Further since gate I5 is controlled by MVI and isoperable only during such time as MVI is operable, that is to say whileoperating cycle of MVl is shown by curve l. The

operating cycle of both MV2 and MVA together (these multivibratorsdetermining the generation of both'sets of equalizing signals) is shownby curve m.

Horizontal synchronizing signal Reference now may be made to thehorizontal synchronizing signals which form a part of the signalradiated. Normally the signals are generated from the action of the 31.5k. c. pulses or pips from tap 13 acting to establish the leading edge ofthe pulses and signals or pulses, or pips as they may be termed, fromtap I I4 of delay line I3 acting to establish the rears of the signalsthrough gate 25. It will be apparent, however. that during interval titino horizontal synchronizing pulses should be developed. This may beaccomplished by taking off from MVI a voltage having a wave shape asindicated in curve g of Fig. 2 and using the voltage to keep gate 25closed during the equalizing and vertical synchronizing signalgeneration period. The multivibrators are triggered on for a shortperiod of time titi once per field of scanning and the recurring signaldeveloped within MVI may be utilized to determine both the intervalsduring which the equalizing and vertical synchronizing signals aredeveloped, and also/develop a control for eliminating generation ofhorizontal synchronizing signals during this interval.

Gate circuit normally is open, or conducting, and through this gatecircuit the pips from tap I I4 of the delay line pass to synchronizinggenerator 2| to establish the rears of the horizontal synchronizingsignals. During time titi, however, a negative voltage may be taken fromMVI and used, when impressed on gate circuit 25, to render this gateinoperative, and, hence, prevent the generation of horizontalsynchronizing signals during this interval of time. When MVI is off thesignals are generated in a normal fashion.

It has been stated that in the practical embodiment of this inventionthe phase of the rear edge of the signal from the differentiatingnetwork and which has been developed from the 2H long 60 cycle signalfrom the timer unit is slightly out with respect to one of the 31.5 k.c. pips (see curve d of Fig. 3). The reason for this is that normallyduring a cycle of operation the 6 counter, having to deliver threepulses, must have eighteen pulse intervals in which to do this. If thephase of the 31.5 k. c. pip and the rear edge of the differentiatedsignal from element 42 were the same, the first pip might pass throughgate I5 simultaneously with MVI and MV2 going on at time t1. It is tokeep the 6 counter from being responsive to this initial pip that thephase of one of .these two signals is selected so that the 6 counterdoes not start counting until approximately at the end of one intervalbetween two of the 31.5 k. c. pips. To this extent therefore theinterval titz is not equal to interval tzt: and tati, the latter twobeing equal.

Horizontal synchronizing signal deletion Since the horizontalsynchronizing signals have.

been developed from the pulses or pips having a 31.5 k. c. frequency andfurther since during the interval between the time t4 and the time t1 ahorizontal synchronizingpulse is developed for each of the pipsgenerated (this time being a complete cycle of operating time with theexception of the interval titi) it will be' apparent that twice as manyhorizontal synchronizing signals are being developed as are usable. Thisis due to the fact that there are 262% lines to the field of scanningand there are 60 fields scanned per second. A frequency of 31.5'k. c.bears an even relationship with respect to the 60 cycle field frequency.It is necessary. therefore, to delete alternate horizontal pulses.

For this purpose there is developed from the 31.5 k. c. pips a wavewhich may be used as a deleting wave. For this purpose a multivibrator28 is provided which has fed thereto (by means of conductor 26) the 31.5k. c. pip from the zero tap on the delay line I3. This is a flip floptype of multivibrator and the output wave form thereof is shown incurves k and l of Fig. 2. These curves represent the voltage variationsdeveloped by the multivibrator during alternate scanned fields. 'I'hesemay be combined with the operating signal of gate 29 and the result iscurves m and n of Fig. 2. These signals are effective during alternatefields to control horizontal synchronizing signal output. These signalsare passed through a gate circuit 29 and since the gate 29 is operativewhen MVI is off, and this is during the time titi, the signals from themultivibrator 28 may be impressed onto the gate circuit 22 during timetiti, the latter being a gate for deleting the alternate horizontalsynchronizing signals and having fed thereto the signals fromsynchronizing signal generator 2|. This gate may be considered a form ofmixing circuit in which the circuit is non-conducting if either of thewaves impressed thereon for mixture is suillciently negative in value.Referring to curve 7', Fig. 2, there is shown, partially broken away,the horizontal synchronizing signals developed' (only four being shownfor space reasons), the vertical synchronizing signals (again only fourbeing shown) and the both sets of equalizing signals (again only fourbeing shown of each). 'I'his wave form will be impressed onto one gridof the multigrid tube of the' mixing circuit 22. A curve such as shownin curve m of Fig. 2 (and which is the effective output curve of gate29) will be impressed onto the other grid of the tube. The result willthen be that alternate horizontal synchronizing signals will be deletedduring the negative half cycles of the output Wave form of circuit 28.Curve m represents the wave form impressed onto one grid of the gate 22during the scanning of one field of the image but since this circuitrelates particularly to odd line interlacing, the curve n of Fig. 2 willbe impressed onto one of the grids of the multi-grid mixing tube ofcircuit 22 during the scanning of alternate fields. Apparentdisplacement between these two curves is brought about by therelationship between the number of lines scanned, namely 525 to thecomplete picture, and the number of fields scanned per second which is60. The type of mixing circuit that is used will be shown hereinafter inFigure 11. y

Accordingly, for alternate fields of scanning there will appear in theoutput circuit of the k. c. pips is constant, the relative phase of allvof the developed signals illustrated must be fixed and constant.

Receiver blanking signals In the generation of the blanking signalsassociated with this apparatus, those for the kinescope or receivingapparatus will.be considered rst. Pulses from the` tap 46 on the delayline I3 are conducted to a gate circuit I8. Also conducted to the 4gatecircuit is the signal from the multivibrator 28 which also acts todelete alternate horizontal synchronizing pulses. Since the gate I8 willbe conducting only whenthe Wave from the multivibrator 28 is positive inpolarity (this being a type of mixing circuit), it will be apparent thatonly half of the pulses from the tap 46 will pass through the gate.These pips then will be of a frequency of 15.75 k..c. and will beconstant in phase. These pips then are fed to a well known form ofmultivibrator circuit which may start its cycle when one ofthe pulses isimpressed thereon and which is of a selfn'estoring type of multivibratoras contradistinct from the flip-flop or non-self-restoringtypes ofmultivibrators which have been referred to up to this point of thespecification. The normal time period of the multivibratoryis abouttwice as much in present practice than that of the horizontalsynchronizing signals. These signals therefore are fixed in phase withrespect to the synchronizing signals and since 28 is not operatingduring time titi, the gate I8 is held closed during this period.

The vertical blanking generator for developing the vertical blankingsignal for the kinescope is actuated by a differentiated wave from the60 cycle output section in the timer. The 60 cycle rectangular wavederived from the timer has a positive component which is approximatelythe length of two scanning lines in time or 2H. The positive portion ofthe cycle is differentiated and one of the pips so formed is used to keya multivibrator of the self-restoring type and an output wave which is41/2 to 9% of the length of a field scanning time is developed,occurring at a rate of sixty cycles per second. The multivibrator ismade adjustable so that the width of the blanking signal may be varied.

Signals from the horizontal blanking generator 6l and the verticalblanking generator 63 are mixed as shown hereinafter in Figure llc. Theoutput of circuit 62 is fed to a clipping circuit 66 by means ofconductor 65 and the output of the clipping circuit 66 gives thecomple-te kinescope blanking signal.

The length 2H which is twice the scanning time of a normally scannedline and which has been referred to as the length of the positiveportion of the rectangular wave obtained from the timer in thedevelopment of the blanking signals, was selected in order that alaboratory type of oscilloscope can easily be used for monitoringpurposes with this apparatus.

Transmitter driving signals The multivibrator which generates the waveform for deletion of alternate horizontal synchronizing signals also isused to delete alternate signals which furnish the horizontal drive forthe cathode ray scanning tube, or, in this case, an iconoscope ormonoscope. This generator has been referred to hereinbefore as aso-called flip-flop multivibrator and will Vbe shown more fullyhereinafter in Fig. 11.

Pips of 31.5 k. c. frequency are delivered from tap 68 on delay line I3and are impressed onto gate circuit 30. The output of the gate isimpressed onto the iconoscope horizontal drive generator 52 to establishone of the edges of the output signal thereof. The generator 52 is aflip-flop type of multivibrator producing a rectangular wave. The frontof the wave may be determined by the signal which flips the generatorand the trailing edge of the wave may be determined by the pulse whichrestores or flops the generator back to its Iinitial state. The gate 30is operated by the output wave from multivibrator 28, and which thegenerator for de- 'leting alternate horizontal synchronizing signals.The result will be that alternate pips impressed` on gate 30 will beeffectively deleted.

The relative Wave form produced by multivibrator 28 for each eld ofscanningis indicated at lead 3|.

Gate 26 `also is provided, which is controlled by both the signals fromthe multivibrator 28 and the 31.5 k. c. pipsfrom tap Ill. The result isthatv both the leading edge pips and the pips for establishing thetrailing edge of the driving signal for the iconoscope will, inalternate instances, be deleted since gate 26 also iis operable underthe in-uence of multivibrator 28. The generator 52 will operate underthe control of both gate circuit 30 and gate circuit 26 each of whichwill conduct pips of a frequency of 15.75 k. c. The output of circuit 52then is impressed onto a, clipping circuit 53 (well known) and theoutput thereof is fed to a utilization circuit (indicated but nowshown).

If the horizontal driving signals are to be fed over cables long enoughto cause appreciable delays, as may be the case in supplying a distantpick-up tube, it is possible to change the settings' of the leading 'andtrailing edges thereof' by moving the taps on the delay line from whichthe triggers are secured. The output has been of a negative polarity andhas measured about 5 volts peak to peak across 72 ohms. Its length hasbeen about 7% of the scansion time of a single line.

In the case of the vertical iconoscope drives, a single.` stroke, orself-restoring form of multivibrator may be used. This multivibrator maybe triggered by the differentiated resultof a rectangular wave havingone component thereof of a length equal to approximately twice thelength of the scanning time of a. single line and which has beenreferred to hereinbefore with reference to.the generation of thevertical synchronizing signals. The sixty cycle Wave so differcntiatedis obtained from the timer unit. The output of the multivibrator IM ofFig. 5 will be a rectangular wave having the length of its positive andnegative components governed by the time constants of the RC circuits ofthe multivibrator which generates it, and which will be shownhereinafter in Figure 11. Accordingly, its width may be governed bymaking at least one of the time constant circuits involved adjustable invalue. The output of the multivibrator generator may be clipped andamplified

